The tunnel crossing active fault is severely damaged under the action of fault dislocation. Considering the "economic and safety" principle in engineering design, the tunnel damage should be effectively reduced. In this work, a two-level design method for fault dislocation was proposed and the Urumqi subway tunnel in China was chosen as a typical model to deeply investigate its application feasibility. Based on the definition of the design events of different levels and corresponding design goals, threedimensional finite element soil-tunnel models were established to estimate the response of tunnel. Meanwhile, the rationality of soil-tunnel model was judged by tunnel deformation and internal forces distribution characteristics analysis, and the two-level design goals were evaluated by comparing tunnel damage degree and volumes. The results suggest that under the condition of fault dislocation, the tunnel without disaster mitigation method suffers severely shear, tensile-crack, and compressive damage, which may eventually induce the tunnel collapse. The tunnel damage is reduced significantly by adopting the method of flexible joint. For Urumqi subway tunnel with flexible joints, both of the two-level design goals are effectively realized.
a b s t r a c tNumerical analysis of fracture in concrete is studied with a simplified discrete crack method. The discrete crack method is a meshless method in which the crack is modeled by discrete cohesive crack segments passing through the nodes. The cohesive crack segments govern the non-linear response of concrete in tension softening and introduce anisotropy in the material model. The advantage of the presented discrete crack method over other discrete crack method is its simplicity and applicability to many cracks. In contrast to most other discrete crack methods, no representation of the crack surface is needed. On the other hand, the accuracy of discrete crack methods is maintained. This is demonstrated through several examples.
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